Sunday, February 26, 2006

In 1896 Svante Arrhenius, a Swedish chemist, theorized that increasing or reducing the amount of carbon dioxide in the atmosphere might trigger a change in climate worldwide. Cutting the amount in half, he surmised, could lower average temperatures by 5 degrees C and might bring on an ice age. But, was such a big change possible?

A colleague, Arvid Hogbom, had studied the carbon cycle extensively, calculating the amounts of carbon from various sources including those from industrial emissions. Using Hogbom's numbers Arrhenius calculated that a doubling of carbon dioxide would increase global temperature by 5 degrees C, surprisingly close to modern estimates even though he was working under severe handicaps including relatively low calculating power--he used paper and pencil--and limited data.

He also estimated that it would take 2,000 years to get there. (The latest estimates place this event in the middle of the current century.) Of course, Arrhenius shouldn't be blamed for this underestimate given the impossibility of knowing what lay ahead for population growth and industrialization. But, his was the first in what has turned out to be a consistent string of underestimates concerning the pace and severity of global warming.

In 1938 Guy Stewart Callendar, a British engineer and amateur meteorologist, presented data to the Royal Meteorological Society demonstrating the arrival of global warming. He estimated that temperatures would rise by 1 degree C by 2200. Callendar wasn't very concerned about global warming for two reasons. The pace seemed so slow and he believed that increased levels of carbon dioxide would be good for agriculture.

Neither Arrhenius nor Callendar were well received. Climate theory and experimental evidence at the time seemed to demonstrate conclusively that what they were claiming could not happen.

Starting in 1940 the Earth embarked on a long cooling spell that lasted until 1970. This temporary hiatus in global warming led to a debate in the scientific community in the early 1970s about whether the Earth might be headed into a new ice age and not toward any continued warming. (It turned out later that the cooling trend may have been in part due to the huge amount of air pollution produced by the wartime and then postwar industrial boom, pollution which tended to reflect sunlight back into outer space.)

In 1979 the National Academy of Sciences offered an estimate that doubling of carbon dioxide levels in the atmosphere might lead to warming between 1.5 degrees C and 4.5 degrees C. In 2001 the Intergovernmental Panel on Climate Change (IPCC) estimated that the Earth could warm by between 1.4 degrees C and 5.8 degrees C by 2100. But, these estimates now seem too conservative. What we know today about the masking effects of particulate air pollution, our subsequent successful efforts to reduce them, and the rapid melting of polar ice indicates that the top end of the IPCC estimates will likely have to be raised, perhaps to somewhere between 7 degrees C to 11 degrees C.

Scientists are by nature inclined to claim only what their data and their models allow them to claim. When they get more data, they simply modify their models and plug in their new data. What the history of global warming modelling tells us so far is that we should be prepared for more surprises--on the upside.

(Some of the above information was taken from a delightful and lively history of global warming entitled, "The Discovery of Global Warming." Supplemental material regarding the book is available online in searchable form here.)

Monday, February 20, 2006

Models that predict climate change or energy supplies far into the future are routinely trotted out to explain either that we need to act urgently or that there is nothing to worry about. Why should this be so? Aren't models supposed to tell us the odds of a particular outcome and aren't those odds calculable by any objective observer? The answer is that it depends on what you model and how complete your information is.

For example, the range of results from the roll of a single die is known in advance, i.e., integers one through six inclusive. The result can never be seven or 20 or 0. With this kind of simple system, where all the possible results are known in advance, any guess about any set of rolls of the die are essentially decisions made under risk. But, with almost all real world systems, we cannot know all the possible results in advance. When we run a climate model or a model concerning energy supplies, we are modeling aspects of the world for which many of the variables are unknown (especially those relating to the future) and for which many of the exact relationships of the known variables are not completely understood. If we make policy decisions based on such models, we are making decisions under uncertainty. In short, we do not know anything like the precise odds of our models being "right." They are more scenarios than "results."

It is what we don't know that can hurt us according the Taleb. Taleb is a hedge fund manager and author of an excellent layman's guide to risk entitled "Fooled by Randomness." He skewers Wall Street pitchmen and analysts for their statistical sloppiness and their pretense that risk in the markets can be easily quantified. He points out that because all possible outcomes of any market or investment cannot be known, all investments are made under uncertainty. Wall Street, however, has long considered markets to be rational and well-behaved and therefore amenable to standard bell curve analysis.

Taleb begs to differ. He believes hidden dangers lie in wait that cannot be anticipated or guarded against in the usual ways. He refers to one type of danger as the "black swan." The idea, borrowed from philosopher David Hume, is that no number of observations of white swans can prove that all swans are white. In other words, no number of observations of the past can prove what the future will be like. (In philosophy, this is known as the problem of induction.) In financial markets, Taleb says, financial models act as if "black swan events," that is, completely unexpected, major market moving events, are very, very rare. They are not so rare as Wall Street assumes, he claims, and they make investing much more risky than it appears.

How does this apply to climate models or models of future energy supplies? These models are very much like the incomplete financial models. In fact, both types of models must take into account economic information. Like their counterparts, these energy and climate models assume that patterns discovered in the past can be projected into the future confidently. In practice, few climate scientists will claim that their models provide accurate predictions, only possible scenarios. Unfortunately, many energy analysts, both those who are worried about a nearby peak in world oil production and those who say we have plenty of oil, often portray their models as accurate predictors. When the predicted date of a peak passes without incident, the model is somehow "discredited." But such models are only good for making decisions under uncertainty. There is no clearly known range of possibilities to plug in. Much of the data about future conditions is just conjecture.

Does that mean such models are useless? Not at all. But we must interpret them carefully. Because they are replicas, they do not encompass every possibility. Some possibilities that are unknown may arrive unannounced and result in both positive or negative surprises. The cornucopians are particularly fond of citing how the marketplace and technology have always provided whatever we need in terms of energy and other resources to overcome any presumed environmental limit. In "Fooled by Randomness" Taleb observes, "it does not matter how frequently something succeeds if failure is too costly to bear." The failure to have alternatives to oil in the wake of a nearby oil peak may indeed be "too costly to bear." Cornucopian prognosticators are essentially admitting this by always citing a date far into the future when oil production will peak. The implied message: "We have plenty of time to prepare...but, if I'm wrong, we're screwed."

While those who fear we are headed for major energy shortages or a climate catastrophe in the near future may be premature, they actually offer the kind of advice that Taleb might: "Since the consequences could be so extreme, let's prepare now."

Since no models for climate or energy can possibly be expected to make precise predictions, we should use them to inform us in general terms about what we might face. Taleb says, "In other words, one need not actually compute the alternative histories [or futures] so much as assess their attributes." (Italics are mine.)

And, if one of those alternative futures is the collapse of civilization as we know it, perhaps we should not concern ourselves so much with discovering the precise day it will happen. Perhaps we should take out some insurance now--just in case.

Sunday, February 12, 2006

A thoughtful reader of my previous post, Lobster Boil: The Curious Response to Global Warming's Arrival, emailed a minor objection that some places such as Minnesota (which I mentioned in the piece) are likely to benefit from global warming. He claimed the state will have milder weather and by extension a longer, warmer growing season. Farmers might have to plant different crops, but maybe not.

For Minnesota, alas, not all modellers predict this benign outcome. One model suggests that Minnesota and indeed most of the continental United States will experience increasingly frequent and prolonged droughts. The modelling was the work of David Rind of the Goddard Institute for Space Studies. Rind concluded that climate change models underestimate the intensification of drought because they do not have detailed enough models of land surfaces. His rather troubling conclusions were discussed recently in The New Yorker magazine's "Climate of Man" series.

While global warming is now an accepted fact and human activities, particularly the burning of fossil fuels, are almost certainly the most prominent driver, the future course of that warming remains highly uncertain. Global warming models are exquisitely sensitive to assumptions about future emissions of greenhouse gasses which are, in turn, linked to population growth, economic activity, the use of renewable energy sources, and advances in technology that might mitigate such emissions.

Even more uncertain than the general course of global warming are effects on specific areas. Minnesota may seem more like Missouri and Arkansas by the end of this century, or it may seem more like the Mohave Desert. The issue of water is especially critical in assessing whether there will be any "winners" from global warming. Some places may get more rainfall, but at the wrong time. For instance, snowmelt runoff will decrease in many places significantly as snowfall increasingly turns to rain in winter. That means more runoff in winter and less in the spring and summer when it is more likely to be needed for irrigation and other purposes.

Rind also points to the the problem of adaptation. This is because global warming is a moving target. Minnesota will not suddenly warm to the balmy temperature of St. Louis and stop. Instead, the state will get there in steps with warming every decade that will bring new challenges for adaptation every few years. And, Minnesota and other places won't stop warming at the end of the century. On current projections, the world will keep getting warmer for a long time after that. Here is what Rind told The New Yorker:

“I gave a talk based on these drought indices out in California to water-resource managers,” Rind told me. “And they said, ‘Well, if that happens, forget it.’ There’s just no way they could deal with that.”

He went on, “Obviously, if you get drought indices like these, there’s no adaptation that’s possible. But let’s say it’s not that severe. What adaptation are we talking about? Adaptation in 2020? Adaptation in 2040? Adaptation in 2060? Because the way the models project this, as global warming gets going, once you’ve adapted to one decade you’re going to have to change everything the next decade.

“We may say that we’re more technologically able than earlier societies. But one thing about climate change is it’s potentially geopolitically destabilizing. And we’re not only more technologically able; we’re more technologically able destructively as well. I think it’s impossible to predict what will happen. I guess - though I won’t be around to see it - I wouldn’t be shocked to find out that by 2100 most things were destroyed.” He paused. “That’s sort of an extreme view.”

Rind admits, of course, that his models are not reality, just projections. But, precisely because of the uncertainty in modeling that far into the future, we should be cautious about accepting the notion that we can define future "winners" and "losers" as a result of global warming. Indeed, those who turn out to be "winners" may find themselves inundated by migrants from areas that end up "losers" because of the rise in sea-level (or disasters associated with that rise), droughts and floods, and agricultural devastation.

Without having to accept Lovelock's fatal diagnosis, one can at least acknowledge that he is reminding us that we are all in this together. To imagine that global warming is a game with "winners" and "losers" may be the surest way to make losers of us all.

Sunday, February 05, 2006

In southeastern Minnesota where I recently gave a couple of talks, ice fishing shacks normally dot the many lakes this time of year. Cross-country skiing and ice-skating are everyday activities in winter. And, those not inclined to winter sports are normally forced to participate in the universal winter recreation of snow shoveling.

But, this is not a normal winter in Minnesota, nor indeed in the whole upper Midwest. On a lake near where I was staying, only one lone ice fishing shack could be seen just off the shore. My host said the ice was simply too thin for anyone to venture beyond that point.

How curious then that the response of many Minnesotans to the warmest winter in decades was to say how lovely the weather is. There are those like my friend, of course, who are disappointed that all their usual winter activities are curtailed. But even an ice-skating instructor whom I met at a coffee shop complained on the one day it got below freezing that it was too bad the weather had suddenly gotten so cold! This from a Minnesotan for whom 20 degrees can seem like a heat wave in the dead of winter.

The proximate cause of this warm weather has been the failure of the jet stream to dip down from Canada into the United States. But the longer-term cause can no longer be ignored as we have just concluded the warmest year on record. Global warming has arrived in Minnesota, and the consensus opinion is in: It's great!

It is here where the troubling tale of delayed feedbacks enters the story. The global warming we are experiencing today is the result of greenhouse gasses spewed into the atmosphere as of 30 years ago. And, since the rate of release for such gasses has only increased since that time, we can expect some rather nasty results 30 years hence. Perhaps Minnesotans believe that three decades from now they will be celebrating their state's new status as a tropical paradise. More likely, they will wonder about the grain harvest which is so critical to the Minnesota economy, a harvest increasingly likely to be devastated by droughts. They will wonder whether the mild winters are worth the exceedingly hot summers that will regularly take the lives of many who are frail but cannot afford the mandatory air-conditioning. They will wonder whether they should have looked so idly upon the myriad coal trains that passed through the state every day en route to the Midwest's many coal-fired power plants.

We are like the proverbial lobster sitting in cold water in a pot on the stove; the warmth that comes from the flame underneath at first seems welcome. As the temperature rises, the poor lobster moves aimlessly in the pot enjoying the new climate. Finally, gradually, without any announcement, the temperature exceeds the lobster's tolerable range and he or she becomes dinner. Of course, to save the lobster one would only have to turn the burner off before the water reaches the critical temperature. While turning a burner off only takes a second, turning off global warming will not be so easy; it could take a generation or two, and then only if we are very serious about it.

It is we who are now in the pot as the temperature slowly rises across the globe. But our bodies are giving us a deceptive signal. The warm winter weather seems like a gift, rather than a curse, from nature--even to those who accept global warming as real and potentially very dangerous.

It is a gargantuan effort for the mind to contradict the body and tell us that something which seems so pleasant now will be our undoing. But, human beings are uniquely capable of this, and, in truth, that capability is our only hope.